MT migration: keeping onclick attributes in content? (2 posts)

I'm migrating from MT 2661 to WP 202. So far I've been able to solve all of my problems but this one using plugins and hacks (more plugins than hacks I'm happy to say).

I've been using MT's popup image link feature in my blog to post photos and I noticed on import to WP that all onclick attributes are lost (using both the mt.php distributed with WP202 and the one from Joshua Zader which preserves post ID's).

I believe that my problem has something to do with the filter "content_save_pre", is this true? Is there a plugin or a hack for undoing this? or Where is the code for this filter so I can find a solution myself?